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Full text of "Common liver fluke in Hawaii (Distoma hepaticum"

7 



Hawaii Agricultural Experiment Station, 



HONOLULU 



J. G. SMITH, Special Agent in 



PRESS BULLETIN No.§£? 




THE COMMON LIVER FLUKE /J&A>IVAZ/. V&V* 

X*^ &&/ 

(Distoma hepaticum ) ^rVfffflfHlft '^ 

The fact that 990 cattle out of 3,376 slaughtered for the Hono- 
lulu market during- a period of six months in 1902 showed an 
infection of the liver-fluke and that in certain districts this para- 
site has become epizootic among cattle, calls for a brief compila- 
tion concerning the disease, its cause, transmission and remedies. 
An earlier record places the number of fluky cattle killed for mar- 
ket still higher. "In some parts of Oahu nearly all the cattle 
have been destroyed by the disease ; the sheep from dry districts, 
however, are not affected. Of 602 calves examined at Honolulu, 
298 were found infested; of 2,186 cattle, 1,313 were infested, so 
that about four-sevenths of the animals were diseased.""' 

The disease is not confined to cattle, and because of its varying 
symptoms, duration and variety of hosts has received numerous 
common names, the most familiar of which are, perhaps, the 
"sheep-rot" and "liver-rot." The hosts of the adult of this species 
are man, cattle, sheep, swine, cats, rabbits, horses, goats, deer, 
and other vertebrates, and during one phase of its intermediate 
development, certain fresh-water snails (Mollusca). The disease 
caused by this parasite has been especially destructive to sheep 
with the injury to cattle and swine next in importance. From 
reports it would seem that in no other portion of the United 
States has its attack on cattle been as serious as in Hawaii. 

What the common liver-fluke is: — The parasite is one of the 
flat-worms (Trematoda) known to science as Distoma hepaticum. 
In appearance it is perfectly flat, unsegmented and leaf-like 



* Bulletin 19. Bureauf Df Animal, lad uqti'y, US nppnrtrp ent of Agri- 



r ^wmm, 



culture. 189S, p. 42. / DQgUMgNTfi f)ftt>T 



U.S. DEPOSITORY 



and the specimens taken from infected cattle varied from J inch 
to I inch in length. (See Plate I. G and H.) It infests in cattle 
the liver, gall-bladder, bile-ducts, and has been found in the lungs. 

Tlie life history of the common liver-fluke: — (See Plate I.) 
The' life-history of the fluke is a very complicated affair, occupy- 
ing from 10 to 12 weeks. A brief statement of the important 
phases is sufficient for the purposes of this paper. The eggs (see 
Plate I. A and B) of an adult fluke, numbering from 37,000 to 
45,000, pass from the liver of the infested stock, through the bile- 
ducts to the stomach and then to the intestine, from which they 
are expelled with the faecal matter and, to further develop, must 
fall or be washed into water. In water, and water only, there 
develops within the Qgg a ciliated embryo which finally bursts 
through the eggshell and swims actively about. To further de- 
velop this organism must find or come in contact with certain 
fresh-water snails. Two species of these intermediate hosts are 
recorded from these Islands, Limnaea oahuensis (see Plate I. 
I and J) and Limnaea rubella. The former species occurring on 
Oahu and Maui and the latter on Oahu and Kauai.* 

It is probable that one or both species are generally distributed 
over the Islands, but if certain districts are free from these species 
the stockmen of those districts have certainly reason for self-con- 
gratulation, since because of their part in the transmission of the 
liver-fluke disease, their presence is equally as dangerous to the 
interests of the ranchers as the presence of the fluke itself. To 
continue with the life-history, — these swimming ciliated embryos 
(miracidiitm), (see Plate I, C, ) minute in size, bore their way 
into the body of the snail, if fortunate enough to find a host, and 
seek lodgment in the liver or other parts of the body. Here 
another change in the life-cycle occurs. The organism becomes 
quiet and forms what is known as a sporocyst. (See Plate I, D.) In 
this inactive state each sporocyst gives rise to from 5 to 8 organisms 
within itself called rcdiac. These rediae may be considered a sec- 
ond generation of the immature liver-fluke which leave the spor- 
ocyst when fully developed and seek the liver of the snail, if not 
already lodged there. Within the liver of the snail there is still 
another multiplication of individuals, that is, each redia (see 
Plate I. E.) gives rise to from 12 to 20 further organisms known 



* Fauna Hawaiiensis. Vol. II. Part IV, pp. 392, 393. 



as cercariae. This further development makes still a third gen- 
eration. The cercariae pass from the body of the snail into the 
water and attach themselves to blades of grass (see Plate I. F.) 
or such plants as may occur in or about any standing water; or, 
during a time of high water, they may be carried out on the 
range and. when the water recedes, left on the grass some dis- 
tance away ; or, again, they may be washed from the higher levels 
to fields below. On becoming attached to the blades of grass or 
the stems of other plants, the cercariae become encysted, or dor- 
mant again, and so remain for an indefinite period, until swal- 
lowed with the grass or other forage plant eaten by the stock. 
Local infection has been traced to the feeding to cattle of a much- 
prized forage plant known as hono-hono (Commelina nudiflora), 
which grows abundantly about water-courses throughout the 
Islands. In the stomach of cattle or other animals eating plants 
thus infested with the encysted cercariae, the cyst or covering is 
destroyed and the undeveloped liver-fluke, becoming active again. 
seeks the liver of the host through either the gall-ducts or portal 
veins, and develops into the adult fluke, already mentioned, thus 
completing the life-cycle. 

1 he immense number of eggs and the large increase of each 
intermediate generation would mean an increase of the adult 
fluke almost beyond numbers, were it not for the small chance 
any one individual has of reaching maturity. In the first place, 
few indeed of the eggs in the faecal matter find their way to 
water in which they may hatch into the second stage. Again, 
not all of the resulting ciliated embryos in the water succeed in 
finding the particular fresh-water snails which are their special 
hosts. Failure to find the proper snail results in extermination. 
Finally, not all of the encysted undeveloped flukes on the blades 
of grass are eaten by stock. However, it can be plainly seen that 
where conditions are favorable, that is, where standing water 
abounds where the snails are present and about which fluke- 
infested stock are feeding, the liver-fluke disease can readily 
become epizootic. 

Symptoms of the disease in cattle: — "The first symptoms are 
generally overlooked, the disease not attracting attention until 
the appetite is diminished, rumination (chewing the cud) be- 
comes irregular, the animals become hidebound, and the coat dull 
and staring. The staring coat is due to the contraction of the 
muscles of the hair follicles. The visible mucous membranes be- 



come pale, eyes become dull, there is running at the eyes, and the 
animal gradually becomes emaciated. As the disease advances 
the milk supply is lessened, fever appears, there is generally great 
thirst, but the appetite almost ceases ; oedematous ( dropsical ) 
swellings appear on the belly, breast, etc. ; diarrhoea at first alter- 
nates with constipation, but finally becomes continuous. The dis- 
ease lasts from 2 to 5 months, when the most extreme cases suc- 
cumb."* Animals observed in the last stages of the disease, on 
the windward side of Oahu, could be distinguished from the rest 
of the herd because of their standing alone, with head up and 
apparently without inclination to eat or move. Several post- 
mortems were made and notes taken in regard to the symptoms. 
The blood had become almost free from red corpuscles. Effusion 
of the blood serum had occurred into the abdominal and lung cav- 
ities. In every case enormous numbers of flukes were found in 
the liver, gall-bladder and bile-ducts. In the final stages the res- 
piration becomes rapid and towards the last breathing becomes 
very difficult, due to the extension of the dropsical swellings, 
occurring along the under side of the body to the neck and throat 
so that the animal apparently dies from suffocation and starva- 
tion. 

Determination of the presence of flukes: — The eggs may be 
discovered, if present, by a microscopical examination of the 
faecal matter, or a suspected animal slaughtered and its liver and 
bile-ducts examined for the flukes themselves. If the cattle are 
found to be fluky it would be better to slaughter them for the 
market at once since in the early stages of the disease they have 
a tendency to. fatten, owing to the excessive secretion of the diges- 
tive ferments, and not only would there be a better return for the 
stock but also by destroying the infected organs and contents of 
the intestines, the spread of the disease would be checked. 

Where flukes may be expected to be found: — In general the 
statement is correct that flukes may abound wherever the condi- 
tions are suitable for the life of its intermediate host, the fresh- 
water snail. This would mean any range or pasture containing 
a body of water or marshy place harboring this snail : and, the 
previous introduction of the fluke. Stockmen should be careful 
not to take fluky cattle from place to place and by no means 



* Bulletin 19, Bureau of Animal Industry, U. S. Department of Agri- 
culture. 



purchase stock from a fluke-infested district. A law forbidding 
the sale of infested stock except for the market and providing 
for the inspection of ranges with the power of enforcing the dis- 
use of areas and localities found to be fluke-infested until proper 
precautions were taken would do much towards lessening the 
spread of the disease and checking its serious inroads into the 
herds of these Islands. 

Remedies: — Slaughtering and marketing fluky cattle before the 
last stages of the disease is undoubtedly the most practical method 
of stamping out infection. The liver is the only part of the car- 
cass rendered unfit for food and great care should be taken to 
destroy this organ, the gall-bladder, bile-ducts and contents of 
the intestines. Xo drugs or mixtures have been found by which 
the disease can be successfully treated. However, in case a val- 
uable animal is seriously affected an improved diet together with 
liberal use of stimulants and tonics will in many cases build up 
the system and general vitality so that the animal may live 
through the fourth stage of the disease, when the flukes will die 
or wander out from the infested organs spontaneously. This 
treatment would include the use of cocoanut meal, bran and mill 
feeds, with daily doses of the various iron salts, walnut leaves, 
calamus and gentian. These remedies would only be applicable 
to the treatment of milch cows and fine breeding stock. 

Precautionary measures: — The following preventive measures 
for controling the liver-fluke disease are taken from Bulletin 
Xo. 19 of the Bureau of Animal Industry, United States Depart- 
ment of Agriculture : 

To prevent the scattering of eggs in the fields: 

In buying cattle or sheep, do not purchase any from a fluky herd, as 
they may introduce the disease to your farm. 

If animals are fluked, send those which are most affected to the 
butcher and place the others on dry ground. 

Destroy the livers of the slaughtered animals, or if used as food for 
animals (dogs, etc..) they should first be cooked in order to kill the 
eggs; if this precaution is not taken, the fresh eggs will pass through 
the intestine of the dog uninjured and be scattered over the fields. 

Manure from fluky animals should never be placed upon wet ground. 
It is. however, not dangerous to use such manure upon dry ground. 

As rabbits and hares may introduce the disease into a district, or 
may keep up an infection if once introduced, these animals should be 
kept down as much as possible. This is not always practicable. (This 
precaution does not apply to Hawaii in so far as rabbits and hares are 
concerned but is most important as regards the wild goats and swine.) 

Where animals very heavily infested with flukes have pastured on a 
given piece of ground, some one should go over the field with a spade 
and spread out the patches of manure, so that it will dry more rapidly, 
and thus the eggs may be more quickly destroyed. A spade full of 
lime or dust will aid in drying up the manure patches. (Applies only to 
dairy herds in Hawaii. It is a good point to mention in this connection 
that this practise will also be fatal to the eggs of the horn-fly. depos- 
ited in the fresh manure by the adult fly.) 

Manure of fluky animals should not be stored where it can drain into 
pastures, 



To control marshy ground: 

The marshes should be drained, if possible, so that the snails may 
be gotten rid of. 

It has been noticed that sheep which pasture on salt marshes are 
not fluked; accordingly dressings of salt, to which lime may be added, 
should be spread over the pasture, as salt and lime will destroy the 
embryos, the encysted cercariae, and the snails. . . . 

Lime will destroy the grass for immediate use, but will in some 
cases be advantageous to the soil. . . . 

If the marshy ground cannot be controlled, place the animals on 
higher ground. (This also does not generally apply to Hawaiian con- 
ditions, since in many places the constant moisture of the higher alti- 
tudes renders the conditions ideal for the life of the snail and the 
development of the parasite.) 

To destroy the snail. — This may be done by draining the fields, thus 
depriving the snails of the conditions necessary for their development, 
or by the free use of salt and lime. 

General precautions to be taken: 

It is known that salt will kill the cercariae; accordingly if salt is 
given to the animals they stand a better chance of escaping hepatic 
(fluke) infection, even if the germs are swallowed, not only because 
this substance kills the young flukes, but because it aids the animals 
in their digestion. (The value of feeding salt to fluke-infested stock 
has been proved by experiments noted in this connection but which 
are not quoted.) 

A daily allowance of dry food should be given. 

If fields are overstocked the animals will be obliged to graze very 
close to the ground, and will thus be more liable to become infected, 
accordingly, in order to prevent this close grazing, fields should not be 
overstocked. 

Animals should not be left too long upon the same pasture. 

Raised watertanks .should be placed in the pastures so that the herds 
will not be forced to drink from pools, etc. As it is difficult for snails 
to get into such drinking tanks, there will be little fear of infection 
from tanks of this sort. 



Tared G. Smith, 
D. L. Van Dine. 



Honolulu, T. H., January 5. 1905. 



EXPLANATION OF PLATE I. 



The Life-Cycle of the Liver-Fluke, Distoma hepaticum. A. — Egg of 
the common liver fluke containing a developed embryo. Magnified 130 
diameters. B, — Egg after hatching. C,— The ciliated embryo ae it 
appears before attacking the fresh-water snail. Magnified about 350 
diameters. D, — A sporocyst which has developed from the embryo 
within the body of the snail, in which may be seen the developing 
rediae. Magnified 200 diameters. E, — Redia in the liver of the snail 
with developed cercariae. Magnified 150 diameters. F, — Encysted 
cercariae on a portion of a grass stalk. Magnified 10 diameters. 
G, — Young of liver fluke which has developed from cercariae in liver 
Of stock. Natural size. H, — Adult liver fluke from liver of stock. 
Natural size. I and J, — The fresh-water snail, Limnaea oahuensis, an 
intermediate host of the liver fluke. Slightly enlarged. (A, B, C, G 
and H copied from Neuman's Parasites and Parasitic Diseases of 
Domesticated Animals. D, E, F, I and J copied from Bulletin 19, 
Bureau of Animal Industry, U, S. Department of Agriculture.) 




PLATE I. 



UM/VER S/ 



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